Chain problems with eng swap..???

I swapped the enging from one of my bikes, now I have a problem with the chain "walking" off the rear sprocket to the 'inside" of the sprocket between spokes and sprocket. I set the chain on the front sprocket and the rear sprocket to "eye" up the "run" . The small front sprocket is further "in" and causes a "diagonal run" which throws the chain off.... how can I remedy this?... I tried to remove the front sprocket thinking I could "shim" it out... never did get it off... then I thought I'd remove one of the washers off the rear wheel but after consideration I realized that would not change the "relationship" of rear to front sprocket... anyone have any solutions? who has experienced similar issues?... remedy?..... thanks
Bob

Cant you just use washers on your axel to move your wheel over? The other alt. would be to make a thinner rag joint that goes between the sprocket and the spokes.....

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"No such thing as a stupid question, just a stupid answer"

48cc Grubee Starfire Round Head......

you could check and see if the main shaft bearings are seated in the housing of the engine there is a lip that the bearing bottom out on and yours might not be seated or the shaft might have been machined a little off.
I have noticed that the rear mount on these engines have a little off set on the aluminum block that bolts between the engine and bike frame see if you have that on so the off set is correct.
I've found that the rear sprocket will allow more side to side wobble and the chain will stay on but if yo get the sprocket mounted where the wobble is up and down it will make you have a bad day as the chain will go tight then very slack. Just some things to drive you crazy.
Norman

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norms-iron-works.tripod.com

Thanks for the replies and input. Misteright I did look at that outer rag joint, and thought about washer tinkering on the wheel... thinking the rag joint is "holding the sprocket out of align".. but wouldn't have a clue what to use for a thinner replacement. Norman thanks for the suggestions and info on the offset of mount... I'll try again...